tube prototyping safety

[Doug Tymofichuk]

On Sun, 2 Jan 2000 20:53:31 +0100 jhaible 
<jhaible at debitel.net> wrote:

> Hi,
> 
> I was wondering about safety in building tube circuits,
> especially about grounding.
> 
> I think there is no doubt that on the *finished* device 
> there should be protective earth (PE) attached to the metal 
> enclosure, (and probably to the signal ground as well).

Funny you should ask, I just did myself. Definitely the 
metal enclosure or chassis needs to be earth grounded, but 
I have heard differing opinions on signal ground.
 
> But what are you doing while prototyping, when you're
> working on the open circuit ? My thought would be *not* to 
> attach protective earth anywhere and keep the high DC 
> voltage floating, so you'd only run into danger when you're 
> touching both the high voltage and the signal gnd at the 
> same time. (With parts of the circuit connected to PE you'd 
> be in danger just touching *one* point of the circuit.)
> 
> Is this the way to go ? Or am I very wrong here ?

I agree with this method, I have been prototyping this way 
myself without problems. AFAIK this is also the correct way 
to service line powered devices like televisions, where the 
entire piece of equipment is isolated via bench transformer 
so that all points are floating with respect to earth.

Please correct me if I am wrong.
----------------------
Doug Tymofichuk
dougt at cancerboard.ab.ca